1. Field of the Invention
The present invention relates to graft cured compositions containing unsaturated ester-modified elastomeric polymers and their preparation through interactions with reactive monomers.
2. Description of Related Art
It is known in the prior art that certain elastomeric polymers containing conjugated diene unsaturation can be graft cured by reacting such polymers with one or more free radically polymerizable monomers in the presence of a free radical initiator. For example, U.S. Pat. No. 3,968,185 teaches that elastomers such as dehydrohalogenated copolymers of isobutylene and isoprene (butyl rubber) or elastomeric terpolymers of ethylene/propylene and a 5,6-dialkylene-2-norbornene can be crosslinked by reacting the elastomer with a free radically polymerizable monomer such as styrene in the presence of a free radical initiator. The presence of free internal diene unsaturation in such elastomers facilitates the addition of monomer chains onto the polymer backbone and the formation of complex polymer networks, some of which are grafted networks connecting different elastomeric molecules. These crosslinkable compositions can be formulated to provide cured products having an unusual balance of physical properties and are useful as coatings, adhesives and in molded and extruded mechanical, automotive and industrial goods.
Analogs of halogenated butyl rubber have been recently discovered which comprise the halogenation product of a random copolymer of a C.sub.4 to C.sub.7 isomonoolefin, e.g. isobutylene, and a para-alkylstyrene, e.g. para-methylstyrene, such as disclosed in U.S. Pat. No. 5,162,445. Although these materials are devoid of olefinic backbone unsaturation, the presence of a benzylic halogen, e.g. bromine, permits facile crosslinking or curing of the polymers using zinc oxide/stearic acid curing systems. In addition, functionalized versions of these copolymers may be prepared by nucleophilic substitution of the benzylic halogen present in the polymer molecules with a reagent reactive therewith to provide polymers containing amine, acid, ester, amide and the like functionality. Grafted polymers may also be prepared by a graft-onto reaction wherein the halogenated copolymer is reacted in solution with a polymeric nucleophile such as polystyryl lithium. These graft-onto reactions lead to the production of solvent soluble grafted copolymers but do not provide crosslinked grafted copolymers analogous to those described above.